What is the role of genetic testing in the diagnosis of medullary thyroid carcinomas (MTC)?

Updated: May 09, 2018
  • Author: Pramod K Sharma, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

Genetic testing is now the mainstay in the diagnosis of the FMTC syndromes. RET proto-oncogene mutations (on chromosome arm 10q) have been discovered in each of the MTC syndromes. The RET proto-oncogene is a receptor tyrosine kinase whose exact function and role in these syndromes has not been elucidated. Patients with MEN 2A have germline RET mutations resulting in substitutions of conserved cysteine residues in exons 10 and 11. All patients with MEN 2B have a germline mutation resulting in a threonine-for-methionine substitution in codon 918 of exon 16. Mutations are described in exons 13 and 14 in patients with FMTC.

Genetic screening with sensitive PCR assays for germline RET mutations is routinely performed in at-risk patients. Children of parents known to have MEN or FMTC are tested for RET mutations to guide therapy and future genetic counseling. In addition, patients presenting with sporadic MTC should undergo RET mutational analysis to rule out new spontaneous germline mutations, which should prompt the testing of offspring for similar mutations.


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